1. Field of the Invention
The present invention generally relates to a flat-panel display device including a matrix array of display pixels, and more particularly to a flat-panel display device in which each of the display pixels has a memory element for storing image data.
2. Description of the Related Art
In recent years, active matrix liquid crystal display panels have been widely used as a monitor display for a note PC or a mobile communication terminal in view of excellent display and high reliability as a product. The liquid crystal display panel is generally formed of an array substrate in which a plurality of pixel electrodes are arrayed in a matrix, a counter substrate in which a counter electrode disposed to face the pixel electrodes and a liquid crystal layer held between the array substrate and the counter substrate. The array substrate includes, in addition to the pixel electrodes, a plurality of scanning lines disposed along rows of the pixel electrodes, a plurality of signal lines disposed along columns of the pixel electrodes and a plurality of pixel switches disposed near intersections of the scanning lines and the signal lines. Each of the pixel switches is connected so as to apply a signal voltage of a corresponding signal line to a corresponding pixel electrode when driven via a corresponding scanning line. With a use of the pixel switches, a crosstalk between neighboring pixels can be sufficiently reduced and an image with high contrast can be obtained.
The pixel switch is generally formed of a thin film transistor having a semiconductor thin film of amorphous silicon. Recently, as a result of progress in manufacturing technology, the semiconductor thin film can be of polysilicon, whose carrier mobility is higher than the amorphous silicon. With the thin film forming technique, not only the pixel switches for pixel electrodes, but also a vertical driver and a horizontal driver, for example, can be formed on the array substrate.
As mobile communication terminals such as a portable phone or the like generally operate by power from a battery, it is preferable that power consumption is as low as possible. To suppress the power consumption, the brightness of a display screen is usually decreased while the portable phone is in a standby state waiting for an incoming call. In recent years, there is another known technique of causing the vertical driver and the horizontal driver to be unused. With this technique, a plurality of memory elements are disposed in display pixels constituting the display screen and store image data representing a static image to be displayed in the standby state. The vertical driver and the horizontal driver are suspended while the static image is displayed based on the contents of the memory elements. As a result, power consumption of display can be suppressed.
Nevertheless, when the vertical driver and the horizontal driver are fully suspended, it is difficult to update part of the displayed image.
In light of the above-described technical drawbacks, an object of the present invention is to provide a flat-panel display device which can update part of display image at low consumption power.
According to one aspect of the present invention, there is provided a flat-panel display device comprising: a matrix array of display pixels which respectively have memory elements and display an image corresponding to contents of the memory elements; a vertical scanning circuit which selectively designates row blocks of the display pixels to enable writing into the memory elements corresponding to a designated row block; a horizontal scanning circuit which selectively designates column blocks of the display pixels to write image data into the memory elements corresponding to a designated column block; an interface which accesses a video memory for each display pixel to set and retrieve address and image data supplied externally; and a controller which controls the vertical scanning circuit and horizontal scanning circuit with reference to the address data and image data supplied from the interface; wherein the interface has an operation mode of detecting address data for part of the display pixels corresponding to the image data supplied externally and different from the image data stored in the video memory, determining a rewriting range of the row and column blocks including the part of the display pixels specified by detected address data, and supplying partial image data corresponding to the rewriting range to the controller.
With the flat-panel display device, addressing of the vertical scanning circuit and the horizontal scanning circuit can be simplified since the interface determines a rewriting range of the row and column blocks including part of the display pixels specified by address data corresponding to image data supplied externally. Thus, even if the part is short for rewriting to each block of the display pixels, shortage of image data can be supplemented by the contents of the video memory. Namely, when image data of an addressing form is externally supplied to update part of the image data stored in the video memory, the addressing form can be adapted for an addressing system of the controller. Accordingly, a part of the displayed image can be updated without requiring power consumption as compared with the case where the memory elements of all the display pixels are rewritten.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.